Hospital beds may include a base frame, an elevatable frame whose height can be adjusted relative to the base frame, a deck comprising one or more orientation adjustable deck sections, and a mattress supported by the deck. One type of deck has a head or upper body section corresponding to an occupant's back neck and head, a seat section corresponding to the occupant's buttocks, a thigh section corresponding to the occupant's thighs, and a calf section corresponding to the occupant's calves and feet. All of the sections except the seat section are orientation adjustable. Adjustments made to one of the adjustable deck sections changes the orientation of the portion of the mattress resting on that deck section. One known type of mattress is an air mattress comprising one or more inflatable bladders.
When the head section undergoes a change of orientation from a horizontal (0°) orientation to a non-horizontal orientation, interior portions of the occupant's body, particularly the skeleton, typically translate toward the foot of the mattress. However, friction at the occupant/mattress interface can prevent the occupant's skin and other soft tissue from undergoing a corresponding translation. As a result, the soft tissue becomes stretched. The resulting shear stress on the occupant's skin, particularly if sustained over a long period of time, is associated with skin breakdown due to, for example, interference with blood flow, lymphatic function and shearing of the dermal/epidermal layer.
It is, therefore, desirable to develop beds, mattresses, and methods to relieve the shear and tissue stretch associated with changes in the orientation of the head section or other orientation adjustable components of the bed.